After getting the old girl uncovered recently, I decided to try to tune her up with a vacuum gauge. Last fall I replaced my distributor and didn't really get a chance to tune it before winterizing. When I summerized I plugged in the vacuum gauge and it was fluttering suggesting worn valve guides or sticking valves (?) -- see video below.

So a few days ago I dumped some Marvel Mystery Oil in the crankcase and let her run for a while over the last couple of days. I figured it couldn't hurt.

Tonight I found some Sea Foam in my garage and decided to drizzle that into the carb throat while at fast idle. I did that for a little while and then revved it up...

Suddenly my vacuum reading went way up. Like... it's steady at 25 inches now!!?! This seems like almost too much vacuum (it's above the 'normal' range on my gauge).

Timing was 10 BTDC for both clips in this video.

The first 12 seconds of the following video was shot last week. The remaining video was shot this evening.

What the hell is going on here? Did I free up a sticking valve or something? Engine experts or amateurs please chime in.